<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>缓存全局变量</title>
</head>
<body>
    <input type="button" value='btn' id='btn1'>
    <input type="button" value='btn' id='btn2'>
    <input type="button" value='btn' id='btn3'>
    <p>111</p>
    <input type="button" value='btn' id='btn4'>
    <input type="button" value='btn' id='btn5'>
    <p>222</p>
    <input type="button" value='btn' id='btn6'>
    <input type="button" value='btn' id='btn7'>
    <input type="button" value='btn' id='btn8'>
    <p>33333</p>
    <input type="button" value='btn' id='btn9'>
    <input type="button" value='btn' id='btn10'>
    <script>
        function getBtn() {
            let oBtn1 = document.getElementById('btn1')
            let oBtn3 = document.getElementById('btn3')
            let oBtn5 = document.getElementById('btn5')
            let oBtn7 = document.getElementById('btn7')
            let oBtn9 = document.getElementById('btn9')
        }
        function getBtn2() {
            let obj = document
            let oBtn1 = obj.getElementById('btn1')
            let oBtn3 = obj.getElementById('btn3')
            let oBtn5 = obj.getElementById('btn5')
            let oBtn7 = obj.getElementById('btn7')
            let oBtn9 = obj.getElementById('btn9')
        }
        // Jsperf中查看结果
    </script>
</body>
</html>